fix(files): properly handle dropping files

[susnux]

Summary

• resolves [Bug]: Drag&Drop folder upload not working #58454

use upload library for dropped files instead of custom logic

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI

[susnux]

/backport to stable33

[susnux]

it shows the parent folder as one item in the conflict picker, even though it is technically not a file, right? So shouldn't it show the conflict picker for files in the folder itself?

Not sure what you mean? This is only about dropping files onto an existing folder.
It is not changing how drag and drop to the "dropzone" works

[susnux]

Yes but thats not changed by this PR.
This PR is only about dropping files onto existing folders in the file list, not onto the drop zone.

unrelated

[susnux]

/backport to stable32

[susnux]

/compile

[susnux]

/compile rebase

[szaimen]

🐘